#!/bin/bash
#
# usage:
# arp_update:
# Send ipv6 multicast pings to all "UP" L3 interfaces including vlan interfaces to
# refresh link-local addresses from neighbors.
# Send gratuitous ARP/NDP requests to VLAN member neighbors to refresh
# the ipv4/ipv6 neighbors state.

ARP_UPDATE_VARS_FILE="/usr/share/sonic/templates/arp_update_vars.j2"

# Overload `logger` command to include arp_update tag
logger () {
    command logger -i "$$" -t "arp_update" "$@"
}

while /bin/true; do
  # find L3 interfaces which are UP, send ipv6 multicast pings
  ARP_UPDATE_VARS=$(sonic-cfggen -d -t ${ARP_UPDATE_VARS_FILE})
  SWITCH_TYPE=$(echo $ARP_UPDATE_VARS | jq -r '.switch_type')
  TYPE=$(echo $ARP_UPDATE_VARS | jq -r '.type')
  if [[ "$SWITCH_TYPE" == "chassis-packet" ]] || [[ "$TYPE" == "BackEndToRRouter" ]]; then
      # Get array of Nexthops and ifnames. Nexthops and ifnames are mapped one to one
      STATIC_ROUTE_NEXTHOPS=($(echo $ARP_UPDATE_VARS | jq -r '.static_route_nexthops'))
      STATIC_ROUTE_IFNAMES=($(echo $ARP_UPDATE_VARS | jq -r '.static_route_ifnames'))

      if [[ -z "$STATIC_ROUTE_NEXTHOPS" ]] || [[ -z "$STATIC_ROUTE_IFNAMES" ]]; then
          if [[ "$SWITCH_TYPE" == "chassis-packet" ]]; then
              # exit gracefully if running on supervisor/rp
              logger "exiting as no static route in packet based chassis"
              exit 0
          fi
          # continue if running on BT0
      else
          for i in ${!STATIC_ROUTE_NEXTHOPS[@]}; do
              nexthop="${STATIC_ROUTE_NEXTHOPS[i]}"
              if [[ $nexthop == *"."* ]]; then
                  neigh_state=$(ip -4 neigh show | grep -w $nexthop | tr -s ' ')
                  ping_prefix=ping
              elif [[ $nexthop == *":"* ]] ; then
                  neigh_state=$(ip -6 neigh show | grep -w $nexthop | tr -s ' ')
                  ping_prefix=ping6
              fi
              # Check if there is an INCOMPLETE, FAILED, or STALE entry and try to resolve it again.
              # STALE entries may be present if there is no traffic on a path. A far-end down event may not
              # clear the STALE entry. Refresh the STALE entry to clear the table.
              if [[ -z "${neigh_state}" ]] || [[ -n $(echo ${neigh_state} | grep 'INCOMPLETE\|FAILED\|STALE') ]]; then
                  interface="${STATIC_ROUTE_IFNAMES[i]}"
                  if [[ -z "$interface" ]]; then
                      # should never be here, handling just in case
                      logger -p error "missing interface entry for static route $nexthop"
                      continue
                  fi
                  intf_up=$(ip link show $interface | grep "state UP")
                  if [[ -n "$intf_up" ]]; then
                      pingcmd="timeout 0.2 $ping_prefix -I ${interface} -n -q -i 0 -c 1 -W 1 $nexthop >/dev/null"
                      eval $pingcmd
                      # STALE entries may appear more often, not logging to prevent periodic syslogs
                      if [[ -z $(echo ${neigh_state} | grep 'STALE') ]]; then
                          logger "static route nexthop not resolved ($neigh_state), pinging $nexthop on $interface"
                      fi
                  fi
              fi
          done

          if [[ "$SWITCH_TYPE" == "chassis-packet" ]]; then
            sleep 150
            # skip the rest of the script if running on a packet chassis
            continue
          fi
      fi
  fi

  # find L3 interfaces which are UP, send ipv6 multicast pings
  INTERFACE=$(echo $ARP_UPDATE_VARS | jq -r '.interface')
  PC_INTERFACE=$(echo $ARP_UPDATE_VARS | jq -r '.pc_interface')
  VLAN_SUB_INTERFACE=$(echo $ARP_UPDATE_VARS | jq -r '.vlan_sub_interface')

  ALL_INTERFACE="$INTERFACE $PC_INTERFACE $VLAN_SUB_INTERFACE"
  for intf in $ALL_INTERFACE; do
      ping6cmd="timeout 0.2 ping6 -I $intf -n -q -i 0 -c 1 -W 0 ff02::1 >/dev/null"
      intf_up=$(ip link show $intf | grep "state UP")
      if [[ -n "$intf_up" ]]; then
          eval $ping6cmd
      fi
  done

  # find neighbor entries with aged MAC and flush/relearn them
  STALE_NEIGHS=$(ip neigh show | grep -v "fe80" | grep "STALE" | awk '{print $1 "," $5}' | tr '[:lower:]' '[:upper:]')
  for neigh in $STALE_NEIGHS; do
        ip="$( cut -d ',' -f 1 <<< "$neigh" )"
        mac="$( cut -d ',' -f 2 <<< "$neigh" )"
        if [[ -z $(sonic-db-cli ASIC_DB keys "ASIC_STATE:SAI_OBJECT_TYPE_FDB_ENTRY*${mac}*") ]]; then
            timeout 0.2 ping -c1 -w1 $ip > /dev/null
        fi
  done

  # Flush neighbor entries with MAC mismatch between kernel and APPL_DB
  KERNEL_NEIGH=$(ip neigh show | grep -v "fe80" | grep -v "FAILED\|INCOMPLETE" | cut -d ' ' -f 1,3,5 --output-delimiter=',' | tr -d ' ')
  for neigh in $KERNEL_NEIGH; do
        ip="$( cut -d ',' -f 1 <<< "$neigh" )"
        intf="$( cut -d ',' -f 2 <<< "$neigh" )"
        kernel_mac="$( cut -d ',' -f 3 <<< "$neigh" )"
        appl_db_mac="$(sonic-db-cli APPL_DB hget NEIGH_TABLE:$intf:$ip neigh)"
        if [[ $kernel_mac != $appl_db_mac ]]; then
            logger -p warning "MAC mismatch for ${ip} on ${intf} - kernel: ${kernel_mac}, APPL_DB: ${appl_db_mac}"
            ip neigh flush $ip
            timeout 0.2 ping -c1 -w1 $ip > /dev/null
        fi
  done

  VLAN=$(echo $ARP_UPDATE_VARS | jq -r '.vlan')
  SUBTYPE=$(sonic-db-cli CONFIG_DB hget 'DEVICE_METADATA|localhost' 'subtype' | tr '[:upper:]' '[:lower:]')
  for vlan in $VLAN; do
      # generate a list of arping commands:
      #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 1>;
      #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 2>;
      #   ...
      arpingcmd="sed -e 's/ / -i /' -e 's/^/arping -q -w 0 -c 1 /' -e 's/$/;/'"
      ipcmd="ip -4 neigh show | grep $vlan | cut -d ' ' -f 1,3 | $arpingcmd"

      eval `eval $ipcmd`

      # send ipv6 multicast pings to Vlan interfaces to get/refresh link-local addrs
      ping6cmd="timeout 1 ping6 -I $vlan -n -q -i 0 -c 1 -W 0 ff02::1 >/dev/null"
      eval $ping6cmd

      # generate a list of ndisc6 commands (exclude link-local addrs since it is done above):
      #   ndisc6 -q -w 0 -1 <IP 1> <VLAN interface>;
      #   ndisc6 -q -w 0 -1 <IP 2> <VLAN interface>;
      #   ...
      ndisc6cmd="sed -e 's/^/ndisc6 -q -w 0 -1 /' -e 's/$/;/'"
      ip6cmd="ip -6 neigh show | grep -v fe80 | grep $vlan | cut -d ' ' -f 1,3 | $ndisc6cmd"
      eval `eval $ip6cmd`

      if [[ $SUBTYPE == "dualtor" ]]; then
        # capture all current failed/incomplete IPv6 neighbors in the kernel to avoid situations where new neighbors are learned
        # in the middle of the below sequence of commands
        unresolved_kernel_neighbors=$(ip -6 neigh show | grep -v fe80 | grep $vlan | grep -E 'FAILED|INCOMPLETE')
        failed_kernel_neighbors=$(echo "$unresolved_kernel_neighbors" | grep FAILED | cut -d ' ' -f 1)

        # it's possible for kernel neighbors to fall out of sync with the hardware
        # this can result in failed neighbors entries that don't have corresponding zero MAC neighbor entries
        # and therefore don't have tunnel routes installed in the hardware
        # flush these neighbors from the kernel to force relearning and resync them to the hardware:
        # 1. for every FAILED or INCOMPLETE neighbor in the kernel, check if there is a corresponding zero MAC neighbor in APPL_DB
        # 2. if no zero MAC neighbor entry exists, flush the kernel neighbor entry
        #     - generates the command 'ip neigh flush <neighbor IPv6>' for all such neighbors
        unsync_neighbors=$(echo "$unresolved_kernel_neighbors" | cut -d ' ' -f 1 | xargs -I{} bash -c "if [[ -z \"\$(sonic-db-cli APPL_DB hget NEIGH_TABLE:$vlan:{} neigh)\" ]]; then echo '{}'; fi")
        if [[ ! -z "$unsync_neighbors" ]]; then
            ip_neigh_flush_cmd="echo \"$unsync_neighbors\" | sed -e 's/^/ip neigh flush /' -e 's/$/;/'"
            eval `eval "$ip_neigh_flush_cmd"`
            sleep 2
        fi

        # generates the following command for each FAILED or INCOMPLETE IPv6 neighbor
        # timeout 0.2 ping <neighbor IPv6> -n -q -i 0 -c 1 -W 1 -I <VLAN name> >/dev/null
        if [[ ! -z "$unresolved_kernel_neighbors" ]]; then
            ping6_template="sed -e 's/^/timeout 0.2 ping /' -e 's/,/ -n -q -i 0 -c 1 -W 1 -I /' -e 's/$/ >\/dev\/null;/'"
            failed_ip6_neigh_cmd="echo \"$unresolved_kernel_neighbors\" | cut -d ' ' -f 1,3 --output-delimiter=',' | $ping6_template"
            eval `eval "$failed_ip6_neigh_cmd"`
            # allow some time for any transient INCOMPLETE neighbors to transition to FAILED
            sleep 5
        fi

        # manually set any remaining FAILED entries to permanently INCOMPLETE
        # once these entries are INCOMPLETE, any subsequent neighbor advertisement messages are able to resolve the entry
        # ignore INCOMPLETE neighbors since if they are transiently incomplete (i.e. new kernel neighbors that we are attempting to resolve for the first time),
        # setting them to permanently incomplete here means the kernel will never generate a netlink message for that neighbor
        # generates the following command for each FAILED IPv6 neighbor
        # ip neigh replace <neighbor IPv6> dev <VLAN name> nud incomplete
        failed_kernel_neighbors=$(ip -6 neigh show | grep -v fe80 | grep $vlan | grep -E 'FAILED')
        if [[ ! -z "$failed_kernel_neighbors" ]]; then
            neigh_replace_template="sed -e 's/^/ip neigh replace /' -e 's/,/ dev /' -e 's/$/ nud incomplete;/'"
            ip_neigh_replace_cmd="echo \"$failed_kernel_neighbors\" | cut -d ' ' -f 1,3 --output-delimiter=',' | $neigh_replace_template"
            eval `eval "$ip_neigh_replace_cmd"`
        fi
      fi
  done


  # sleep here before handling the mismatch as it is not required during startup
  sleep 300

  # refresh neighbor entries from APP_DB in case of mismatch with kernel
  DBNEIGH=$(sonic-db-cli APPL_DB keys NEIGH_TABLE*)

  # resolve neighbor entries from CONFIG_DB in case of mismatch with kernel
  DBNEIGH="$DBNEIGH $(sonic-db-cli CONFIG_DB keys NEIGH* | sed -e 's/|/:/g')"

  KERNEIGH4=$(ip -4 neigh show | grep Vlan | cut -d ' ' -f 1,3  --output-delimiter=',')
  KERNEIGH6=$(ip -6 neigh show | grep -v fe80 | grep Vlan | cut -d ' ' -f 1,3  --output-delimiter=',')
  for neigh in $DBNEIGH; do
      intf="$( cut -d ':' -f 2 <<< "$neigh" )"
      ip="$( cut -d ':' -f 3- <<< "$neigh" )"
      if [[ $intf == *"Vlan"* ]]; then
          if [[ $ip == *"."* ]] && [[ ! $KERNEIGH4 =~ "${ip},${intf}" ]]; then
              pingcmd="timeout 0.2 ping -I $intf -n -q -i 0 -c 1 -W 1 $ip >/dev/null"
              eval $pingcmd
              logger "mismatch arp entry, pinging ${ip} on ${intf}"
          elif [[ $ip == *":"* ]] && [[ ! $KERNEIGH6 =~ "${ip},${intf}" ]]; then
              ping6cmd="timeout 0.2 ping6 -I $intf -n -q -i 0 -c 1 -W 1 $ip >/dev/null"
              eval $ping6cmd
              logger "mismatch v6 nbr entry, pinging ${ip} on ${intf}"
          fi
      fi
  done

done
